Bone resorption in edentulous subjects provides a challenge in many aspects of dental restorative procedures. For instance during drill and implant guided surgery a surgical template is placed directly on the mucosa. However, in edentulous subjects a defined, stable position of the surgical template may be not given, e.g. due to bone resorption of the alveolar ridge. Furthermore, there may be no unambiguous anatomical structure in the oral cavity giving a clear-cut positioning of the surgical template in the subject. The same issue may occur at other cranial sites, e.g. when planning facial reconstructions, such as including ear, nose, or eye prosthesis.
Hence, when a surgical template is fixed to a subject, the position of the surgical template may differ largely from a desired position, e.g. pre-determined in a virtual planning based on input data related to a position of a structure having a defined position to the subject's anatomy during data acquisition, such as a radiographic guide. Positioning of the real surgical template manufactured based on data of the virtual planning is thus difficult. This may inherently lead to a non-desired positioning of implants in the subject, and thus non-desired results of surgical restorative procedures, such as dental restorative procedures.
In US2007077535 a method is disclosed dealing with this issue. The disclosed method is a model-based dental restorative method relying on the use of positioning screws having fixed positions. The disclosed method is a purely mechanical method where the positioning screws serve as temporary posts intended to provide reliable positioning of e.g. drilling templates. A conventional, plaster cast based production of drilling templates is disclosed, wherein the positioning screws are screwed into the lingual-oral or palatal area (i.e. the oral area of the lower or upper jaw oriented towards the tongue) and/or into the alveolar process (the thickened ridge of bone that contains tooth sockets) so that an impression of the position of the positioning screws and capturing the actual structure of the patient's jaw is taken. Subsequently, corresponding positioning screws are installed in the impression; and finally any further technical dental work is carried out on the impression, namely the manufacture of a drilling template for the implants to be installed. The drilling template thus manually created is positioned in the oral cavity of the patient by snapping it onto the positioning screws that thus serve as re-positioning aides.
However, the method disclosed in US2007077535 is purely model based, and has a number of drawbacks.
For instance, a surgical template is produced in a conventional model-based manner, whereby sources of errors as conventionally known are not eliminated, e.g. shrinkage of each of an impression material and subsequently of a casting material for a surgical template cast form and finally the material of the surgical template in the cast are contributors to an error chain, whereby accuracy is lost in each process step. This lack of accuracy may not be acceptable in some medical procedures.
Therefore, the method disclosed in US2007077535 may not work satisfactory, in particular for critical applications, such as implantation of zygoma implants.
Further, a mass customization of surgical templates to be used in dental restorative procedures is not feasible according to the method disclosed in US2007077535. Each single surgical template needs an enormous amount of manual adaptation on physical casts and models.
Hence, an improved method and system for facilitating or providing precise repositioning of components related to cranial surgical procedures, such as dental procedures in at least partly edentulous subjects, e.g. suffering from bone resorption, would be advantageous.